MODEL STUDIES OF HYDROPORPHYRIN-CONTAINING ENZYMES

这项研究计划的目的是加深对 它的结构、电子和机械特性 含氢卟啉的酶。这些都催化了关键的重要步骤 代谢过程包括无机碳、氮和硫 微生物的循环和许多主要的能量产生途径。 该计划有两个具体目标：(1)确定有意义的 氢卟啉络合物性质的差异， 以及(2)开发反应性模型 依赖于F430的甲基辅酶M还原酶的还原裂解 变成甲烷。人工合成的酶活性部位的小分子类似物 在这些研究中将使用假体小组。第一 AIM将通过测试以下假设来实现： 氢卟啉、科林斯和其他四吡咯的区别在于 它们的灵活性以及最优孔尺寸和孔尺寸范围 在它们的络合物中很容易获得，并且取代基 立体化学可以调节大循环的性质。这个 假设将通过检查化学过程来检验，这些化学过程需要 金属离子半径的变化或四聚吡咯的变形 大循环。饱和程度和取代基的影响 大环轴向连接平衡的立体化学和 大半径金属离子如镍(I)和铜(I)的可及性将是 调查过了。将通过调查来调查飞机外的灵活性 大环饱和度对芳香基势垒的影响 N-取代四芳基氢卟啉中的环旋转 R-Co(P)L钴-烷基键离解能的关联 对于大环，P和反式配体的立体主体L 第二个目标将通过探索NII(OEiBC)的反应来实现。 重点将放在确定氢化物物种在 NiI(OEiBC)的化学，检测镍配合物的能力 甲基辅酶M等硫醚化合物的分离及烷基镍的检测 和氢化镍OEiBC络合物。

The objective of this research program is to develop an understanding of the structural, electronic, and mechanistic features of the hydroporphyrin-containing enzymes. These catalyze important steps in key metabolic processes including the inorganic carbon, nitrogen, and sulfur cycles and many of the main energy producing pathways of microorganisms. The program has two specific aims: (1) to determine the significant differences in the properties of the complexes of hydroporphyrins, porphyrins, and other tetrapyrroles and (2) to develop a reactivity model for the F430 dependent reductive cleavage of methyl coenzyme M reductase to methane. Synthetic, small molecule analogues of enzyme active sites and prosthetic groups will be used in these investigations. The first aim will be addressed by testing the hypotheses that porphyrin, hydroporphyrins, corrins, and other tetrapyrroles are distinguished by their flexibility and by the optimal hole size and range of hole sizes readily accessible in their complexes and that the substituent stereochemistry can modulate the properties of the macrocycle. The hypotheses will be tested by examining chemical processes that require changes in metal ion radius or deformation of the tetrapyrrole macrocycle. The effect of the saturation level and substituent stereochemistry of the macrocycle on axial ligation equilibria and the accessibility of large radius metal ions like Ni(I) and Cu(I) will be investigated. Out-of-plane flexibility will be probed by investigations of the effect of the macrocycle saturation level on the barrier to aryl ring rotation in N-substituted tetraarylhydroporphyrins and by correlations of the cobalt-alkyl bond dissociation energies of R-Co(P)L with the macrocycle, P, and the steric bulk of the trans ligand, L. The second aim will be achieved by exploring the reactions of NiI(OEiBC). Emphasis will be placed on determining the role of hydride species in the chemistry of NiI(OEiBC), examining the ability of nickel complexes to cleave thioethers like methyl coenzyme M, and the detection of alkyl-Ni and hydrido-Ni OEiBC complexes.